Idarucizumab is a fully humanized antigen-binding fragment (Fab) of an antibody binding to the active metabolite (dabigatran) of the anti-coagulant prodrug dabigatran etexilate [4]. Idarucizumab has been granted FDA Breakthrough Therapy Designation to help expedite its development, as it represents a solution to an unmet clinical need. That is, to be able to reverse the effects of newer direct, oral anticoagulants such as dabigatran etexilate on demand. Antidotes to other direct anticoagulants in development are discussed in [3] and [1] (see also andexanet alfa).The crystal structure of dabigatran-bound idarucizumab has been resolved at 1.7Å (Protein Data Bank ID 4JN2) [5]. Additional information regarding the invention of idarucizumab is available in patent US8486398 [6].